Crustal versus mantle sources of granitic magmas: a two-parameter model based on Nd isotopic studies

DePaolo, Donald J.; Perry, Frank V.; Baldridge, W. Scott

doi:10.1130/spe272-p439

Cited by 44 publications

(15 citation statements)

References 23 publications

(19 reference statements)

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“…Table 4. Neodymium crustal index (NCI) calculations (DePaolo et al 1992) for the felsic rocks of the YTT in the Finlayson Lake region. signatures may be a common feature to prospective felsic successions in bimodal silicaclastic VMS environments (e.g., Whalen et al 1998;Lentz 1999;Piercey et al 2001a).…”

Section: Implications For Vms Mineralizationmentioning

confidence: 99%

Neodymium isotope geochemistry of felsic volcanic and intrusive rocks from the YukonTanana Terrane in the Finlayson Lake Region, Yukon, Canada

Piercey¹,

Mortensen²,

Creaser³

2003

Can. J. Earth Sci.

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DevonianMississippian felsic rocks from the Finlayson Lake region have variable geochemical and Nd isotopic characteristics that provide insights into the tectonic and metallogenic evolution of the YukonTanana terrane (YTT), and the northern Cordillera. Late Devonian (~365360 Ma) calc-alkaline and tholeiitic arc felsic rocks in the mafic-dominated Fire Lake unit yield εNd350 = 4.8 and +0.1, respectively, and have 1.491.94 Ga depleted mantle model ages (TDM). DevonianMississippian (~360356 Ma) felsic volcanic (Kudz Ze Kayah unit, Wolverine succession) and intrusive rocks (Grass Lakes suite) associated with volcanogenic massive sulphide (VMS) deposits have εNd350 = 7.8 to 9.5 with TDM = 1.592.25 Ga. A granitoid sample from the Early Mississippian (~350345 Ma) Simpson Range plutonic suite has εNd350 = 12.9 and TDM = 2.01 Ga, similar to previously reported values for this suite. The VMS-associated Grass Lakes suite of granitoids has higher high field strength element (HFSE) and rare-earth element (REE) contents, and higher Zr/Sc, Zr/TiO2, Nb/La, and Zr/La values relative to the Simpson Range plutonic suite; these geochemical features are similar to coeval VMS-associated felsic volcanic rocks in the Kudz Ze Kayah unit. The identification of similar HFSEREE-enriched felsic volcanic and subvolcanic intrusive rocks may aid in delineating prospective regions for VMS mineralization in the YTT and other continental-margin arc to back-arc environments. The geochemical and Nd isotopic data for these YTT felsic rocks suggest that they reflect episodic mid-Paleozoic arc (Fire Lake unit; Simpson Range plutonic suite) and back-arc magmatism (Kudz Ze Kudz unit; Wolverine succession) built upon a transitional basement with variable, but significant, influence from evolved (Proterozoic) crustal materials.

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Section: Implications For Vms Mineralizationmentioning

confidence: 99%

Neodymium isotope geochemistry of felsic volcanic and intrusive rocks from the YukonTanana Terrane in the Finlayson Lake Region, Yukon, Canada

Piercey¹,

Mortensen²,

Creaser³

2003

Can. J. Earth Sci.

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“…Kistler, 1974; Reid et al. , 1983; DePaolo et al. , 1992; Poli, 1992; Kerr & Fryer, 1993; Soesoo & Nicholls, 1999; Gagnevin et al.…”

Section: Introductionmentioning

confidence: 99%

Microstructural evidence for magma confluence and reusage of magma pathways: implications for magma hybridization, Karakoram Shear Zone in NW India

Hasalová

Weinberg

MacRae

2011

Journal of Metamorphic Geology

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In the Karakoram Shear Zone, Ladakh, NW India, Miocene leucogranitic dykes form an extensive, varied and complex network, linking an anatectic terrane exposed in the Pangong Range, with leucogranites of the Karakoram Batholith. Mineral paragenesis of the heterogeneous anatectic source rocks suggests melting has resulted from water influx into rocks at upper amphibolite facies conditions, and microstructures suggest anatexis was contemporaneous with shearing. The network is characterized by continuous and interconnected dykes, with only rare cross-cutting relationships, forming swarms and chaotic injection complexes where magmatic rocks cover up to 50% of the outcrop area. Despite this volume of magma, the system did not lose continuity, suggesting that it did not flow en masse and that the magma network was not all liquid simultaneously. Leucogranites in this network, including leucosomes in migmatites, carry an isotopic signature intermediate between the two main anatectic rocks in the source, suggesting efficient homogenization of the magmatic products. Here, we describe a number of microscopic features of these magmatic rocks which suggests that several pulses of magma used the same pathways giving rise to textural and chemical disequilibrium features. These include: (i) narrow, tortuous corridors of fine-grained minerals cutting across or lining the boundaries of larger grains, interpreted to be remnants of magma-filled cracks cutting across a pre-existing magmatic rock; (ii) corrosion of early formed grains at the contact with fine-grained material; (iii) compositional zoning of early formed plagioclase and K-feldspar grains and quartz overgrowths documented by cathodoluminescence imaging; (iv) incipient development of rapakivi and anti-rapakivi textures, and (iv) different crystallographic preferred orientation of early formed quartz and fine-grained quartz. Mapping of the fine-grained corridors interpreted to represent late melt channels reveal an interlinked network broadly following the S-C fabric defined by pre-existing magmatic grains. We conclude that early formed dykes provided a pathway exploited intermittently or continuously by new magma batches. New influxes of magma opened narrow channels and migrated through a microscopic network following predominantly grain boundaries along an S-C fabric related to syn-magmatic shearing. A mixed isotopic signature resulted not from the mixing of magmas, but from the micro-scale interaction between new magma batches and previously crystallized magmatic rocks, through local equilibration.

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“…The , 1986;DePaolo et al, 1992). In either case, the Cassiar magmas bear the imprint of both mafic and felsic sources.…”

Section: Discussion Of Isotope Geochemistrymentioning

confidence: 99%

Petrogenesis of the Cretaceous Cassiar batholith, Yukon-British Columbia, Canada: Implications for magmatism in the North American Cordilleran Interior

Driver

Creaser

Chacko

et al. 2000

Geological Society of America Bulletin

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Bibliothèque nationale du Canada Acquisions and Acquisitions et Bibliographie Services services bibliographiques 395 Weilingbn Street 395. rue Wellington OttawaûiU K 1 A W ûttawa ON K I A ON4 Canada cana& The author has granted a nonexclusive licence allowing the National Libraxy of Canada to reproduce, l o q distribate or selI copies of this thesis in microform, paper or electronic formats. L'auteur a accordé une licence non exclusive permettant à la Bibliothèque nationale du Canada de reproduire, prêter, distribuer ou vendre des copies de cette thèse sous la forme de microfiche/film, de reproduction sur papier ou sur forma: électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fiorn it Ni la thèse ni des extraits substantiels may be printed or otheNvise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation, View northward of the Cassiar batholith and surounding area, from norrhcentral British Columbia, Canada lf we want to be pedantic, al1 granitoids are 'M'-types; some just have longer evolutionary paths than others!-D. B. Clarke

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Crustal versus mantle sources of granitic magmas: a two-parameter model based on Nd isotopic studies

Cited by 44 publications

References 23 publications

Neodymium isotope geochemistry of felsic volcanic and intrusive rocks from the YukonTanana Terrane in the Finlayson Lake Region, Yukon, Canada

Neodymium isotope geochemistry of felsic volcanic and intrusive rocks from the YukonTanana Terrane in the Finlayson Lake Region, Yukon, Canada

Microstructural evidence for magma confluence and reusage of magma pathways: implications for magma hybridization, Karakoram Shear Zone in NW India

Petrogenesis of the Cretaceous Cassiar batholith, Yukon-British Columbia, Canada: Implications for magmatism in the North American Cordilleran Interior

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Crustal versus mantle sources of granitic magmas: a two-parameter model based on Nd isotopic studies

Cited by 44 publications

References 23 publications

Neodymium isotope geochemistry of felsic volcanic and intrusive rocks from the YukonTanana Terrane in the Finlayson Lake Region, Yukon, Canada

Neodymium isotope geochemistry of felsic volcanic and intrusive rocks from the YukonTanana Terrane in the Finlayson Lake Region, Yukon, Canada

Microstructural evidence for magma confluence and reusage of magma pathways: implications for magma hybridization, Karakoram Shear Zone in NW India

Petrogenesis of the Cretaceous Cassiar batholith, Yukon-British Columbia, Canada: Implications for magmatism in the North American Cordilleran Interior

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Neodymium isotope geochemistry of felsic volcanic and intrusive rocks from the YukonTanana Terrane in the Finlayson Lake Region, Yukon, Canada

Neodymium isotope geochemistry of felsic volcanic and intrusive rocks from the YukonTanana Terrane in the Finlayson Lake Region, Yukon, Canada